BAMAKO, Mali  Radical Islamists held on to a city in central Mali on Friday after sending the Malian military reeling in retreat. With the militants showing the capability to press even further into government-held territory, international aid organizations began evacuating staff from the narrow central belt of the country.

French President Francois Hollande said France, which used to rule Mali as a colony, is ready to help to the stop the Islamist extremists. He did not specify what assistance it is prepared to offer. French Defense Minister Jean-Yves Le Drian wrote on his Twitter account Friday: “On the phone with [U.S. Defense Secretary] Leon Panetta about the Malian crisis. This afternoon with my European counterparts.”

Residents who live near an airport about 30 miles from the captured town on Konna reported hearing planes arrive throughout the night. Who, or what, the planes were bringing could not be immediately determined.

The United Nations Security Council condemned the capture of Konna and called on U.N. member states to provide assistance to Mali “in order to reduce the threat posed by terrorist organizations and associated groups.”

A regional military intervention to take back northern Mali from the Islamists was not likely before September, though the advance by the al-Qaida linked forces in the desert nation in northwest Africa creates pressure for earlier military intervention.

“France, like its African partners and the entire international community, cannot accept that,” Hollande said in a speech to France’s diplomatic corps, referring to the Islamists’ advances.

A top French diplomat, who spoke on condition of anonymity because he was not authorized to speak publicly on the matter, said that France is now able to deploy military assets — notably air power — over Mali “very quickly.”